Blow molding polystyrene nanocomposites

ABSTRACT

Disclosed is a polystyrene based polymer/layered compound nanocomposite for injection blow molding or injection stretch blow molding of articles. The nanocomposite can reduce shrinkage and warpage to the preform during the reheating process compared to neat polystyrene. The incorporation of layered compounds can increase the processability of PS preforms, help improve heating efficiency, and improve bottle mechanical properties. The layered compound can be treated with chemicals or compounds having an affinity with the styrene monomer or polystyrene, thus producing a treated layered compound having an affinity with the styrene monomer or polystyrene. The monomer and the layered compound can be combined prior to polymerization. The polymer and layered compound can be combined by solution mixing in a solvent. The layered compound can also be incorporated into the mixture by compounding a polymer product with the layered compound, or the combination of any of the above three approaches

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.12/508,598, filed on Jul. 24, 2009.

FIELD

Embodiments of the present invention generally relate to blow molding ofpolystyrene. In particular, embodiments of the invention relate toincorporating a layered compound such as clay nanoplatelets into thepolystyrene for injection stretch blow molding and injection blowmolding of styrene based polymers.

BACKGROUND

In general, a high quality packaging material is one that creates a goodoxygen and moisture barrier. Packaged goods are intended to last longertypically by reducing their interaction with oxygen and water, whichusually can deteriorate the product causing waste and other problems.Polymeric materials are often used as packaging materials because theycreate a good oxygen/moisture barrier and their appearance and shape canbe easily controlled. Plastic materials are also used in place of glassfor bottling because they are lighter, are more resistant to breakagewhen dropped, and can be less expensive. Several common polymericmaterials used for packaging are polyethylene (PE), polyethyleneterephthalate (PET), polypropylene (PP), polycarbonate (PC), andpolystyrene (PS).

Polystyrene is one of the largest volume thermoplastic resins incommercial production today. It is a hydrocarbon chain containing aphenyl group on every other carbon atom. Polystyrene is a durablepolymer that is frequently encountered in daily life. A few commonexamples of polystyrene are plastic toys, computer housings, foampackaging, foam cups, etc.

Injection blow molding (IBM) and injection stretch blow molding (ISBM)are well-developed techniques to produce plastic containers that includethe formation of a perform that is subsequently heated and blow moldedto produce a hollow container. Preforms are generally condensed shapes,which may include relatively thick-walled tube shaped articles having athreaded neck to facilitate appropriate closure. The preforms can beblown into a desired article shape by heating, stretching, and blowingthe preform with a compressed gas. The compressed gas expands thepreform into the shape of the mold.

Polymer nanocomposites comprise polymeric materials and inorganiclayered compounds, such as clay. When these inorganic layered componentsare properly incorporated into a polymer matrix, significantimprovements in physical and mechanical properties can be displayed. Theextent of uniformity of the layered compound incorporated into thepolymer matrix influences the characteristics of the nanocomposite.

A high degree of intercalation (the inserting of a molecule, or group ofmolecules, between a layer of clays) and exfoliation (the delaminationof layered materials into disordered layers or sheets) are desired inorder to achieve proper incorporation of the inorganic layered compoundsinto a polymer matrix. In order to achieve a high degree ofintercalation and exfoliation, the clays can be treated by some organicchemicals to increase their surface hydrophobicity and interlayerdistances. These clays can be referred to as organoclays.

An initial evaluation of polystyrene for blow molding applications ledto shrinkage and warpage issues. It is desirable to have polystyrenecompositions that can minimize shrinkage and warpage during blowmolding.

SUMMARY

Embodiments of the present invention include a preform for use in blowmolding processes of polystyrene based polymer. The preform includes aneck having an internal neck diameter and an external neck diameter, abody comprising an internal body diameter and an external body diameterwhich together form a sidewall, and is made of a nanocomposite includinga polystyrene based polymer and a layered compound.

The layered compound can be selected from the group consisting ofnatural clay, synthetic clay, sols, colloids, gels, and fumes. Thelayered compound can be a treated layered compound formed by treating alayered compound with an organic compound to produce a treated layeredcompound having an affinity with styrene. The layered compound can betreated by a chemical that has an organic group having a solubilityparameter, wherein the difference between the organic group solubilityparameter and the solubility parameter of styrene is no more than 3.0(MPa^(1/2)).

The layered compound can be treated by a chemical that comprises atleast one hydrocarbon ring group, or by a chemical that comprises atleast one methacrylate group. The layered compound can be treated by achemical that is represented by the formula:

where HT is Hydrogenated Tallow (˜65% C₁₈; ˜30% C₁₆; ˜5% C₁₄).

The invention can include an article formed by the blow molding of thepreform described herein. The preform can have a shrinkage of less than38% when reheated during a blow molding process. The preform can have awarpage of less than 8.5% when reheated during a blow molding process.

The layered compound incorporated within the preforms can help absorbenergy, thus improving reheating efficiency. As a result, embodiments ofthe invention can include preforms made of nanocomposites that can reacha temperature of at least 5° F. higher than an identical preform withoutthe layered compound when reheated during a blow molding process underthe same conditions.

Embodiments of the present invention include a method of forming a blowmolded article by providing a nanocomposite comprising a polystyrenebased polymer and a layered compound, forming a preform from thenanocomposite, heating the preform, and injection blow molding thepreform into an article. The preform has at least one layer of thenanocomposite and can include one or more layers of a polystyrene basedpolymer that is not a nanocomposite. The injection blow molding caninclude injection stretch blow molding the preform into an article. Thelayered compound can be selected from the group consisting of naturalclay, synthetic clay, sols, colloids, gels, and fumes. The method caninclude the layered compound being a treated layered compound formed bytreating a layered compound with an organic compound to produce atreated layered compound having an affinity with styrene.

The layered compound can be treated by a chemical that has an organicgroup having a solubility parameter, wherein the difference between theorganic group solubility parameter and the solubility parameter ofstyrene is no more than 3.0 (MPa^(1/2)). The layered compound can betreated by a chemical that has at least one hydrocarbon ring group. Thelayered compound can be treated by a chemical that has at least onemethacrylate group.

The layered compound can be treated by a chemical that is represented bythe formula:

where HT is Hydrogenated Tallow (˜65% C₁₈; ˜30% C₁₆; ˜5% C₁₄).

The method can include heating of the preform resulting in shrinkage ofless than 38% and warpage of less than 8.5%.

The layered compound incorporated within the preforms can help absorbenergy, thus improving reheating efficiency. As a result, embodiments ofthe invention can include preforms made of nanocomposites that can reacha temperature at least 5° F. higher than an identical preform withoutthe layered compound when heated under the same conditions. Theinvention can include an article formed by the method described.

An embodiment of the present invention is a method for production of ablow-molded article having improved morphology, processability andheating efficiency. The method includes mixing polystyrene based polymerwith a treated layered compound to form a polymeric nanocomposite andforming a preform from the polymeric nanocomposite. The preform has atleast one layer of the nanocomposite and can include one or more layersof a polystyrene based polymer that is not a nanocomposite. The preformis heated to a first temperature sufficient for blow molding the preformand injection stretch blow molding the preform into an article. Thetreated layered compound can be formed by treating a layered compoundwith an organic compound to produce a treated layered compound having anaffinity with the polystyrene based polymer prior to mixing. The layeredcompound improves the preform heating efficiency and therefore the firsttemperature is at least 5° F. higher than the temperature of anidentical preform without the layered compound when heated under thesame conditions. The heating of the preform results in a shrinkage ofless than 38% and a warpage of less than 8.5%.

The mixing of the polymer and the treated layered compound can includeat least one of the processes of: compounding the polymer and thetreated layered compound; solution mixing the polymer and the treatedlayered compound in a solvent; or mixing the treated layered compoundwith a styrene based monomer prior to polymerization.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows the bottom of two articles showing non-uniform thicknessand whitening (left) or blow-out (right).

FIG. 2 shows (A) a PS535/10A preform after heating to optimum conditionsfor blow molding; (B) a PS535 preform after heating under the sameconditions as (A); (C) a PS535 preform after heating to desiredconditions for blow molding; and (D) a PS535 preform before heating.

FIGS. 3A and 3B shows a cross sections of a preform illustratingshrinkage and warpage before and after heating, respectively.

FIG. 4 represents a method of preparing a layered compound/polymercomposite involving extrusion compounding.

DETAILED DESCRIPTION

Injection blow molding (IBM) and injection stretch blow molding (ISBM)are well-developed techniques to produce plastic containers that includethe formation of a perform that is subsequently heated and blow moldedto produce a hollow container. Preforms are generally condensed shapes,which may include relatively thick-walled tube shaped articles having athreaded neck to facilitate appropriate closure. The preforms can beblown into a desired article shape by heating, stretching, and blowingthe preform with a compressed gas. The compressed gas expands thepreform into the shape of the mold.

The injection stretch blow molding process can be either a single ordouble stage process. The single stage process injects the moltenpolymer into the preform mold creating the preform, stretches thepreform, and finally blows the preform into the finished shape all inthe same process. In a double stage process, performs are injectionmolded at the first stage. After the preforms are cooled down, they arereheated and subsequently stretched/blow molded into bottles at thesecond stage.

Polystyrene is a material under development for blow moldingapplications. An initial evaluation of polystyrene for ISBM applicationsresulted in a high rejection rate and the molded bottles exhibitedinconsistent properties. Both crystal and high impact polystyrene (HIPS)grades exhibited shrinkage and uneven shrinkage. Moreover, the unevenshrinkage during reheating resulted in warpage along the preform axial(off-center). Such off-centered preforms can give rise to a non-uniformbottle bottom and poor mechanical properties. In addition, the bottlebottom can show signs of whitening, an undesirable characteristic forthe finished part as shown in FIG. 1. Thus, it is important to addressthe shrinkage and warpage issues associated with PS ISBM process.

The incorporation of inorganic fillers, such as layered fillers, mayreduce PS chain relaxation upon reheating by constraining the flexiblechains within the stiff inorganic layers. This effect may be enhanced ifthe filler is incorporated into the matrix on a nanometer scale. Thus,clay based nanocomposites appear to be potential candidates forimproving the processing of PS in IBM and ISBM processes.

As used herein “nanocomposites” refer to materials that are created byintroducing nanoparticles with at least one dimension less than 100nanometers (nm), also called filler materials (e.g., a layered compound)into a macroscopic material (e.g., polymeric material), which iscommonly referred to as the matrix. According to embodiments of theinvention the preform and resulting article from blow molding thepreform comprise a nanocomposite having a layered filler material (alsoreferred to as a nanofiller) and a polystyrene matrix.

The layered compounds can include natural and synthetic clay, sols,colloids, gels, fumes, and the like. In an embodiment, the nanocompositecomprises clay. In accordance with this disclosure, clays refer toaggregates of hydrous silicate particles either naturally occurring orsynthetically produced, and may consist of a variety of minerals rich insilicon and aluminum oxides and hydroxides which include variableamounts of other components such as alkali earth metals and water.Naturally occurring clays are usually formed by chemical weathering ofsilicate-bearing rocks, although some are formed by hydrothermalactivity. These types of clays can be replicated in industrial chemicalprocesses. Many types of clay have sheet-like (layered) structures andthese layers are typically referred to as platelets. These plateletshave a degree of flexibility with a thickness on the order of 1 nm andaspect ratios of 50 to 1500.

The clays used in an embodiment of the present invention can beorganophilic and such clays are typically referred to as organoclay.Organoclay is an organically modified silicate compound that is derivedfrom natural or synthetic clay. Organoclay can be produced from claysthat are typically hydrophilic by ion exchange with an organic cation.Some examples of layered materials suitable as components in organoclaysinclude without limitation natural or synthetic bentonite,montmorillonite, hectorite, fluorohectorite, saponite, stevensite,nontronite, sauconite, glauconite, vermiculite, chlorite, mica,hydromica, muscovite, biotite, phlogopite, illite, talc, pyrophillite,sepiolite, attapulgite, palygorskite, berthierine, serpentine,kaolinite, dickite, nacrite, halloysite, allophane, imogolite,hydrotalcite, pyroaurite, calcite, wollastonite, or combinationsthereof.

Examples of an organoclay suitable for use in this disclosure includewithout limitation CLOISITE 10A, CLOISITE 15A, and CLOISITE 20A, whichare commercially available from Southern Clay Products, Inc.

CLOISITE 10A has the composition that is represented by the formula:

where HT is Hydrogenated Tallow (˜65% C₁₈; ˜30% C₁₆; ˜5% C₁₄); Anion:Chloride;

Cation exchange capacity (CEC): 125 meq/100 g clay.

CLOISITE 15A has the composition that is represented by the formula:

where HT is Hydrogenated Tallow (˜65% C₁₈; ˜30% C₁₆; ˜5% C₁₄); Anion:Chloride; Cation exchange capacity (CEC): 125 meq/100 g clay.

CLOISITE 20A has the composition that is represented by the formula:

where HT is Hydrogenated Tallow (˜65% C₁₈; ˜30% C₁₆; ˜5% C₁₄); Anion:Chloride; Cation exchange capacity (CEC): 95 meq/100 g clay.

In embodiments of the invention, the organoclay may be present in anamount of from 0.1 weight percent (wt. %) to 50 wt. %, alternativelyfrom 0.5 wt. % to 25 wt. %, or from 1 wt. % to 10 wt. %.

In accordance with the invention, the nanocomposite comprises apolystyrene based polymer. The polymer may be present in thenanocomposite in an amount of from 50 wt. % to 99.9 wt. %, or from 90wt. % to 99.5 wt. %, or from 95 wt. % to 99 wt. % based on the totalweight of the nanocomposite.

In an embodiment, the polystyrene based polymer can be formed frommonomers having a phenyl group. More specifically, the polymer can beformed from monomers having an aromatic moiety and an unsaturated alkylmoiety. Such monomers may include monovinylaromatic compounds such asstyrene as well as alkylated styrenes wherein the alkylated styrenes arealkylated in the nucleus or side-chain. Alphamethyl styrene,t-butylstyrene, p-methylstyrene, acrylic and methacrylic acids orsubstituted esters of acrylic or methacrylic acid, and vinyl toluene aresuitable monomers that may be useful in forming a polystyrene basedpolymer of the invention. These monomers are disclosed in U.S. Pat. No.7,179,873 to Reimers et al., which is incorporated by reference in itsentirety.

The polystyrene based polymer component in the nanocomposite can be astyrenic polymer (e.g., polystyrene), wherein the styrenic polymer maybe a homopolymer or may optionally comprise one or more comonomers.Styrene, also known as vinyl benzene, ethenylbenzene, phenethylene andphenylethene is an aromatic organic compound represented by the chemicalformula C₈H₈. Styrene is widely commercially available and as usedherein the term styrene includes a variety of substituted styrenes (e.g.alpha-methyl styrene), ring substituted styrenes such asp-methylstyrene, distributed styrenes such as p-t-butyl styrene as wellas unsubstituted styrenes.

In an embodiment, the styrenic polymer has a melt flow as determined inaccordance with ASTM D1238 of from 1.0 g/10 min to 30.0 g/10 min,alternatively from 1.5 g/10 min to 20.0 g/10 min, alternatively from 2.0g/10 min to 15.0 g/10 min; a density as determined in accordance withASTM D1505 of from 1.04 g/cc to 1.15 g/cm³³, alternatively from 1.05g/cm³ to 1.10 g/cc, alternatively from 1.05 g/cm³ to 1.07 g/cm³, a Vicatsoftening point as determined in accordance with ASTM D1525 of from 227°F. to 180° F., alternatively from 224° F. to 200° F., alternatively from220° F. to 200° F.; and a tensile strength as determined in accordancewith ASTM D638 of from 5800 psi to 7800 psi. Examples of styrenicpolymers suitable for use in this disclosure include without limitationCX5229 and PS535, which are polystyrenes available from TotalPetrochemicals USA, Inc. In an embodiment the styrenic polymer (e.g.,CX5229) has generally the properties set forth in Table 1.

TABLE 1 Typical Value Test Method Physical Properties Melt Flow, 200/5.0g/10 m 3.0 D1238 Tensile Properties Strength, psi 7,300 D638 Modulus,psi (10⁵) 4.3 D638 Flexular Properties Strength, psi 14,000 D790Modulus, psi (10⁵) 4.7 D790 Thermal Properties Vicat Softening, deg. F.223 D1525

In some embodiments, the styrenic polymer or polystyrene based polymerfurther comprises a comonomer which when polymerized with styrene formsa styrenic copolymer. Examples of such copolymers may include forexample and without limitation α-methylstyrene; halogenated styrenes;alkylated styrenes; acrylonitrile; esters of methacrylic acid withalcohols having 1 to 8 carbons; N-vinyl compounds such as vinylcarbazoleand maleic anhydride; compounds which contain two polymerizable doublebonds such as for example and without limitation divinylbenzene orbutanediol diacrylate; or combinations thereof. The comonomer may bepresent in an amount effective to impart one or more user-desiredproperties to the composition. Such effective amounts may be determinedby one of ordinary skill in the art with the aid of this disclosure. Forexample, the comonomer may be present in the styrenic polymer in anamount ranging from 0.1 wt. % to 99.9 wt. % by total weight of thenanocomposite, alternatively from 1 wt. % to 90 wt. %, and furtheralternatively from 1 wt. % to 50 wt. %.

In an embodiment, the polymer or polystyrene based polymer alsocomprises a thermoplastic material. Herein a thermoplastic materialrefers to a plastic that melts to a liquid when heated and freezes toform a brittle and glassy state when cooled sufficiently. Examples ofthermoplastic materials include without limitation acrylonitrilebutadiene styrene, celluloid, cellulose acetate, ethylene vinyl acetate,ethylene vinyl alcohol, fluoroplastics, ionomers, polyacetal,polyacrylates, polyacrylonitrile, polyamide, polyamide-imide,polyaryletherketone, polybutadiene, polybutylene, polybutyleneterephthalate, polychlorotrifluoroethylene, polyethylene terephthalate,polycyclohexylene dimethylene terephthalate, polycarbonate,polyetherimide, polyethersulfone, polyethylenechlorinate, polyimide,polylactic acid, polymethylpentene, polyphenylene oxide, polyphenylenesulfide, polyphthalamide, polypropylene, polysulfone, polyvinylchloride, polyvinylidene chloride, and combinations thereof. Forexample, the thermoplastic material may be present in the styrenicpolymer in an amount ranging from 0.1 wt. % to 50 wt. % by total weightof the nanocomposite.

In an embodiment, the polymer or polystyrene based polymer comprises anelastomeric phase that is embedded in a polymer matrix. For instance,the polymer may comprise a styrenic polymer having a conjugated dienemonomer as the elastomer. Examples of suitable conjugated diene monomersinclude without limitation 1,3-butadiene, 2-methyl-1,3-butadiene, and2-chloro-1,3-butadiene. Alternatively, the thermoplastic may comprise astyrenic polymer having an aliphatic conjugated diene monomer as theelastomer. Without limitation, examples of suitable aliphatic conjugateddiene monomers include C₄ to C₉ dienes such as butadiene monomers.Blends or copolymers of the diene monomers may also be used. Examples ofthermoplastic polymers include without limitation acrylonitrilebutadiene styrene (ABS), high impact polystyrene (HIPS), methylmethacrylate butadiene (MBS), and the like. The elastomer may be presentin an amount effective to impart one or more user-desired properties tothe composition. Such effective amounts may be determined by one ofordinary skill in the art with the aid of this disclosure. For example,the elastomer may be present in the styrenic polymer in an amountranging from 0.1 wt. % to 50 wt. % by total weight of the nanocomposite,or from 1 wt. % to 25 wt. %, or from 1 wt. % to 10 wt. %.

In accordance with the invention, the nanocomposite also optionallycomprises additives, as deemed necessary to impart desired physicalproperties. The additives used in the invention may be additives havingdifferent polarities. Additives suitable for use in the inventioninclude without limitation zinc dimethacrylate, hereinafter referred toas “ZnDMA”, stearyl methacrylate, hereinafter referred to as “StMMA”,and hydroxyethylmethacrylate, hereinafter referred to as “HEMA”.

These additives may be included in amounts effective to impart desiredphysical properties. In an embodiment, the additive(s) are included inamounts of from 0.01 wt. % to 10 wt. %. In another embodiment, whenZnDMA is the additive, it is present in amounts of from 0.01 wt. % to 5wt. %. In another embodiment, when the additive is StMMA or HEMA, theadditive is present in amounts of from 1 wt. % to 10 wt. %.

The chemically treated clay, CLOISITE 10A, has an affinity with styrenemonomers and can exhibit a high degree of exfoliation when added tostyrene, as disclosed in U.S. patent application Ser. No. 12/365,113,incorporated herein in its entirety. CLOISITE 10A, having a benzyl groupattached to it, exhibits high affinity with the benzyl structure ofstyrene. CLOISITE 10A was found to have more structures having a higherdegree of exfoliation within a sample of nanocomposite comprisingstyrene polymer than organoclays not having a benzyl group. Otherorganoclays having hydrocarbon ring structures can have an affinity to astyrenic based monomer and can be desirable for use in the presentinvention. Organoclays having methacrylate groups attached can alsoprovide an affinity to styrenic based monomers.

As used herein two materials have an affinity for each other if there isno more than 3.0 (MPa^(1/2)) difference between their solubilityparameters. CLOISITE 10A contains a benzyl group, benzene having asolubility parameter of 18.8 (MPa^(1/2)) while styrene has a solubilityparameter of 19.0 (MPa^(1/2)). The addition of the organic compound tothe clay, in this instance the benzyl group, provides an affinitybetween the clay and the polymer, as the solubility parameter of thebenzyl group is close to that of the styrene. Other hydrocarbon ringstructures have solubility parameters that would impart an affinity forstyrene, such as cyclohexane with a solubility parameter of 16.8(MPa^(1/2)), cyclopentane with a solubility parameter of 17.8(MPa^(1/2)), and cyclopentanone with a solubility parameter of 21.3(MPa^(1/2)).

As non-limiting examples, Table 2 provides a list of various ringstructured groups and methacrylate groups that may be used to modify alayered compound to provide an affinity between the layered compound andthe monomer or polymer that the layered compound is being dispersedinto. Data in Table 2 is taken from the Polymer Handbook, 4th edition byJ. Brandrup, E. H. Immergut, and E. A Grulke, John Wiley & Sons, Inc.,1999. The solubility parameter can be changed via copolymerization andsolubility parameters for different structures can be calculated via thetechniques given in the Polymer Handbook and published by P. A. Small[J. Applied Chemistry, Vol. 3, p. 71 (1953)] by using molar-attractionconstants.

TABLE 2 Solvent Solubility Parameter (MPa^(1/2)) Butyl methacrylate 16.8Cyclohexane 16.8 Ethyl methacrylate 17.0 Methyl styrene 17.4Cyclopentane 17.8 Chlorotoluene 18.0 Ethylbenzene 18.0 Methylmethacrylate 18.0 Xylene (p-xylene) 18.0 Toluene 18.2 Vinyl toluene 18.6Benzene 18.8 Methylcyclohexanone 19.0 Styrene 19.0 Furan 19.2Chlorobenzene 19.4 Cyclohexanone 20.3 Dichlorobenzene 20.5 Nitrobenzene20.5 Iodobenzene 20.7 Cyclopentanone 21.2 Cyclobutanedione 22.5

In an embodiment, a method for production of the styrenic polymercomprises contacting styrene monomer and other components under properpolymerization reaction conditions. The polymerization process may beoperated under batch or continuous process conditions. In an embodiment,the polymerization reaction may be carried out using a continuousproduction process in a polymerization apparatus comprising a singlereactor or a plurality of reactors. In an embodiment of the invention,the polymeric composition can be prepared for an upflow reactor.Reactors and conditions for the production of a polymeric compositionare disclosed in U.S. Pat. No. 4,777,210, to Sosa et al., which isincorporated by reference in its entirety.

The operating conditions, including temperature ranges, can be selectedin order to be consistent with the operational characteristics of theequipment used in the polymerization process. In an embodiment,polymerization temperatures range from 190° F. to 460° F. In anotherembodiment, polymerization temperatures range from 200° F. to 360° F. Inyet another embodiment, the polymerization reaction may be carried outin a plurality of reactors, wherein each reactor is operated under anoptimum temperature range. For example, the polymerization reaction maybe carried out in a reactor system employing first and secondpolymerization reactors that are either both continuously stirred tankreactors (CSTR) or both plug-flow reactors or one reactor a CSTR and theother a plug-flow reactor. In an embodiment, a polymerization reactorfor the production of a styrenic copolymer of the type disclosed hereinmay comprise a plurality of reactors wherein the first reactor (e.g., aCSTR), also known as the prepolymerization reactor, is operated in thetemperature range of from 190° F. to 275° F. while the second reactor(e.g., CSTR or plug flow) may be operated in the range of 200° F. to330° F.

The polymerized product effluent may be referred to herein as theprepolymer. When the prepolymer reaches a desired conversion, it may bepassed through a heating device into a second reactor to achieve furtherpolymerization. The polymerized product effluent from the second reactormay be further processed as desired or needed. Upon completion of thepolymerization reaction, a styrenic polymer is recovered andsubsequently processed, for example devolatized, pelletized, etc.

In accordance with the invention, the layered compound may beincorporated into the polymer/monomer at any stage of the polymerizationprocess, for example, including without limitation before, during, orafter the polymerization process. In an embodiment, the layered compoundis incorporated by mixing of a monomer with the layered compound. Forexample, by the mixing of styrene monomer with organoclay prior to insitu polymerization. In another embodiment, the layered compound isincorporated by compounding the polymerized product with a layeredcompound. For example, compounding polystyrene with an organoclay. Inyet another embodiment, the layered compound is incorporated by solutionmixing with a polymer, such as polystyrene, in a proper solvent, such astoluene or tetrahydrofuran. For example, solution mixing polystyrenewith an organoclay in toluene.

In an embodiment the layered compound is compounded with a polymer. Insuch an embodiment, in reference to FIG. 5, the method 100 may initiateby contacting the polymer 110 and a layered compound 120 to form amixture via extrusion compounding 130. Extrusion compounding 130 refersto the process of mixing a polymer with one or more additionalcomponents wherein the mixing may be carried out using a continuousmixer such as for example a mixer consisting of a short non-intermeshingcounter rotating twin screw extruder or a gear pump for pumping.

In another embodiment, the polymerized product resulting from in situpolymerization of a monomer with a layered compound is subjected toextrusion compounding 130 to achieve further exfoliation and dispersionof the layered compound. In yet another embodiment, the nanocompositeproduct resulting from a mixed solution comprising polystyrene and alayered compound, which is dried after solution mixing, can be subjectedto extrusion compounding 130 to achieve further exfoliation anddispersion of the layered compound.

Extrusion compounding 130 may produce a composition in which some of thepolymer has been intercalated into the layered compound as depicted instructure 140 a. In structure 140 a, the polymer 110 is inserted betweenplatelets of the layered compound 120 such that the interlayer spacingof the layered compound 120 is expanded but still possess a well-definedspatial relationship with respect to each other. Extrusion compounding130 may also result in some degree of exfoliation as shown in 140 b inwhich the platelets of the layered compound 120 have been separated andthe individual layers are distributed throughout the polymer 110. Themixture of layered compound and polymer after having been extrusioncompounded is hereinafter referred to as the extruded mixture 140 a,b.

The method 100 can also include further processing 150 of the extrudedmixture 140 a,b, such as by imparting shear stresses or orientationforces. The further processing 150 can result in increased exfoliationof the resulting product 160 a,b, where the platelets of the layeredcompound 120 have been further separated and the individual layers aredistributed throughout the polymer 110 providing anintercalated/exfoliated morphology. Although 140 b may have a higherdegree of exfoliation than 140 a, depending on the extent andeffectiveness of the further processing 150, 160 b may or may not have ahigher degree of exfoliation than 160 a.

As disclosed in U.S. patent application Ser. No. 12/365,113, an articleconstructed from a nanocomposite containing a layered compound with thepolymer/monomer showed an improvement in both flexural modulus andYoung's modulus, compared to the polymer lacking the layered compound.Young's modulus is a measure of the stiffness of a material and isdefined as the ratio of the rate of change of stress with strain.Young's modulus can be determined experimentally from the slope of astress-strain curve created during tensile tests conducted on a sampleof a material, as determined in accordance with ASTM D882. In anembodiment, the article made from the nanocomposite may exhibit anincrease in Young's modulus at yield when compared to a similar articleconstructed from a polymer lacking the layered compounds of from 5% to300%, alternatively from 10% to 100%, alternatively from 20% to 50%. Theflexural modulus is another measure of the stiffness of a material andis defined as the amount of applied force over the amount of deflecteddistance. The flexural modulus is measured in accordance with ASTM D790.In an embodiment, the article made from the nanocomposite may exhibit anincrease in flexural modulus when compared to a similar articleconstructed from a polymer lacking the layered compounds of from 5% to300%, alternatively from 10% to 100%, alternatively from 20% to 50%. Inanother embodiment, the article made from nanocomposite may exhibit anincrease in tensile strength at yield, as determined in accordance withASTM D882, when compared to a similar article constructed from a polymerthat does not contain the layered compounds of from 5% to 300%,alternatively from 10% to 100%, alternatively from 20% to 50%.

The optical properties of the nanocomposite containing a layeredcompound are dependent upon the degree of dispersion of the layeredcompound. When the layered compound is well exfoliated and uniformlydispersed, the negative optical effect of the layered compound isminimal. Conversely, poor dispersion of the layered compound in thenanocomposite leads to a significant drop in the clarity of thenanocomposite and the articles made from the nanocomposite.Nanocomposites containing organoclays having an increased affinity withthe styrenic polymer lead to greater exfoliation and are more uniformlydispersed, thereby providing better optical properties.

EXAMPLE

In order to evaluate the effects of the clay based nanocomposites, a PSnanocomposite made from commercially available polystyrene PS535 fromTotal Petrochemicals, Inc. was mixed with 5 wt % of CLOISITE 10A, anorganoclay commercially available from Southern Clay Products, Inc.,herein referred to as 535/10A. The 535/10A mixture was compounded usinga twin-screw extruder and was molded into preforms on a Netstalinjection molder. The preforms were conditioned at room temperature forat least 24 hours before they were stretch-blow-molded into bottles onan ADS G62 linear injection stretch blow molder.

In the ISBM process, the 535/10A preforms exhibited lower shrinkage, andlimited warpage, as compared to preforms of neat PS535. Thus, thepreforms were successfully blow molded into bottles at the fourconditions shown below in Table 3.

TABLE 3 Summary of processing conditions of PS535 and 535/10A preforms.Oven 10 Oven 10 Temperature before and 20, and 20, Oven 20 Oven 20 blowmolding (Oven Preform 2000 b/h 3000 b/h only, 2000 b/h only, 3000 b/h 10and 20, 2000 b/h) PS535 ~50% rejection rate, significant Not 260° F.whitening on the bottom enough heat 535/10A <2% rejection rate, with fewwhitening signs on 246° F. (5 wt %) the bottom

FIG. 3A shows a cross section view of a preform before heating, and FIG.3B shows a cross section view of a preform after heating. The firstpreform length (H₁) and the first body length (h₁) are shown in FIG. 3A.The preform length after heating (H₂), body length after heating (h₂)and amount of deviation (d) are shown in FIG. 3B. Shrinkage is definedas (h₁−h₂)/h₁ and warpage is defined as d/h₂.

FIG. 2 shows (A) a PS535/10A preform after heating to its optimumconditions for blow molding; (B) a PS535 preform after heating under thesame conditions as (A); (C) a PS535 preform after heating to its desiredconditions for blow molding; and (D) a PS535 preform before heating. Theshrinkage of the PS535/10A preform, shown as A, is approximately 20% andthe warpage is virtually zero after heated at its optimized condition,while the shrinkage and warpage of the PS535 preform, shown as C, isabout 40% and 8%, respectively, after heated at its optimized condition.The nanocomposite (A) exhibited significantly reduced shrinkage andwarpage than the neat PS(C) at processing conditions. The nanocompositerequired less heating to achieve processing conditions. The PS535preform (B), subjected to the same heating conditions as thenanocomposite (A), did not absorb the heat as well as the nanocompositeand did not have sufficient heat to achieve blow molding conditions.

TABLE 4 Preform A B C Temp (° F.) 246 218 260 Shrinkage 20 8 40 (%)Warpage 0 0 8 (%)

In addition, it was observed that 535/10A preforms can be blow moldedinto bottles with less heat compared to neat PS535 preforms. Forcomparison, both PS535, shown as C in FIG. 2, and 535/10A, shown as A inFIG. 2, preforms were reheated at their optimized conditions and ameasurement of the surface temperature was made with an IR thermometeras they exited the oven. The 535/10A, shown as A had a temperature of246° F. while the PS535 preform shown as C in FIG. 2 had a temperatureof 260° F. The PS535 preform was also reheated at the optimizedcondition for 535/10A and then tested for surface temperature and had atemperature of 218° F., which is shown as B. At the same heating profile(optimized for 535/10A), the surface temperature of 535/10A preform is28° F. higher than the PS535 preform. At the same time, in order tooptimize the heating for the PS535 preforms, they had to be heated to260° F., which is 14° F. higher than 535/10A preforms.

The 535/10A preforms were successfully blow molded into bottles at aproduction rate of 3000 b/h. However, the same ADS G62 linear injectionstretch blow molder failed to blow mold PS535 preforms at the sameconditions owing to a limited heating capacity. The incorporation ofclay nanoplatelets into the polystyrene matrix is shown to be able toimprove both processability and heating efficiency.

The incorporation of organically modified clay filler can effectivelyreduce preform shrinkage and avoid warpage during the reheating process,which can improve the processability of PS preforms. In addition, it wasalso observed that the heating efficiency and effectiveness wasimproved. The molded 535/10A bottles also exhibit high stiffness. Theaddition of a small amount of clay into PS preforms not only addressesthe processing issue, but can also improve heating efficiency andbottle, properties.

Embodiments of the present invention can include preforms having reheatshrinkage of less than 40%, optionally less than 35%, optionally lessthan 30%, or optionally less than 25%. Embodiments of the presentinvention can include preforms having reheat warpage of less than 8%,optionally less than 6%, optionally less than 4%, optionally less than3%, or optionally less than 2%.

Embodiments of the present invention can include preforms having claynanoplatelets in a PS matrix capable of absorbing IR waves. The preformsof the present invention can reach a temperature higher than that of asubstantially similar preform without clay nanoplatelets under the sameconditions. The temperature can be at least 5° F. higher, optionally atleast 10° F. higher, or at least 15° F. higher than that of asubstantially similar preform without clay nanoplatelets under the sameconditions.

Embodiments of the present invention can include preforms having ananocomposite layer and a non-nanocomposite layer. A preform may have aninner layer of nanocomposite material and an outer layer ofnon-nanocomposite material. Alternately the preform may have an innerlayer of non-nanocomposite material and an outer layer of nanocompositematerial. Alternately the preform may have multiple layers that includeat least one layer of nanocomposite material. An example is a preformthat has an inner layer of nanocomposite material with a skin layer oneach side of a non-nanocomposite material. A co-extrusion stretch blowmolding process is one way of producing a preform having multiplelayers.

Use of broader terms such as comprises, includes, having, etc. should beunderstood to provide support for narrower terms such as consisting of,consisting essentially of, comprised substantially of, etc.

The term “affinity” as used herein shall refer to the tendency of afirst material to mix or combine with a second material of unlikecomposition, such as a solvent and a solute. As used herein twomaterials have an affinity for each other if there is no more than 3.0(MPa^(1/2)) difference between their solubility parameters.

The term “composite materials” refers to materials which are made fromtwo or more constituent materials (e.g., a layered compound and apolymeric material) with significantly different physical and/orchemical properties and which remain separate and distinct on amacroscopic level within the finished structure.

The term “exfoliation” refers to delamination of a layered materialresulting in the formation of disordered layers or sheets.

The term “nanocomposites” refers to materials that are created byintroducing nanoparticulates, also termed filler materials (e.g., alayered compound) into a macroscopic material (e.g., a polymericmaterial), which is typically referred to as the matrix.

Use of the term “optionally” with respect to any element of a claim isintended to mean that the subject element is required, or alternatively,is not required. Both alternatives are intended to be within the scopeof the claim. Use of broader terms such as comprises, includes, having,etc. should be understood to provide support for narrower terms such asconsisting of, consisting essentially of, comprised substantially of,etc.

The term “processing” is not limiting and includes agitating, mixing,milling, blending, etc. and combinations thereof, all of which are usedinterchangeably herein. Unless otherwise stated, the processing mayoccur in one or more vessels, such vessels being known to one skilled inthe art.

Depending on the context, all references herein to the “invention” mayin some cases refer to certain specific embodiments only. In other casesit may refer to subject matter recited in one or more, but notnecessarily all, of the claims. While the foregoing is directed toembodiments, versions and examples of the present invention, which areincluded to enable a person of ordinary skill in the art to make and usethe inventions when the information in this patent is combined withavailable information and technology, the inventions are not limited toonly these particular embodiments, versions and examples. Other andfurther embodiments, versions and examples of the invention may bedevised without departing from the basic scope thereof and the scopethereof is determined by the claims that follow.

1-13. (canceled)
 14. A method of forming a blow molded articlecomprising: providing a nanocomposite comprising a polystyrene basedpolymer and a layered compound; wherein the layered compound is treatedwith an organic compound to thereby form a material having an affinitywith styrene, wherein the organic compound comprises a ring structuredgroup or a methacrylate group selected from the group consisting ofbutyl methacrylate, cyclohexane, methyl styrene, cyclopentane,chlorotoluene, methyl methacrylate, xylene, toluene, vinyl toluene,benzene, methylcyclohexanone, styrene, furan, chlorobenzene,cyclohexanone, dichlorobenzene, nitrobenzene, iodobenzene,cyclopentanone, cyclobutanedione, and combinations thereof; forming apreform having at least one layer made from the nanocomposite; heatingthe preform; and injection blow molding the preform into an article. 15.The method of claim 14, wherein the injection blow molding comprisesinjection stretch blow molding the preform into the article.
 16. Themethod of claim 14, wherein the layered compound comprises natural clay,synthetic clay, sols, colloids, gels, or fumes.
 17. (canceled)
 18. Themethod of claim 14, wherein a difference between a solubility parameterof the ring structured group or the methacrylate group and a solubilityparameter of styrene is no more than 3.0 (MPa^(1/2)). 19-21. (canceled)22. The method of claim 14, wherein the heating of the preform resultsin a shrinkage of less than 40% and a warpage of less than 8%.
 23. Themethod of claim 14, wherein the layered compound improves the preformheating efficiency and the preform reaches a temperature at least 5° F.higher than an identical preform without the layered compound whenheated under the same conditions.
 24. The method of claim 14, whereinthe preform includes at least one layer of the nanocomposite and atleast one layer of polystyrene based polymer that is not ananocomposite.
 25. An article formed by the method of claim
 14. 26. Amethod for production of a blow molded article having improvedmorphology, processability, heating efficiency, and article propertiescomprising: mixing polystyrene based polymer with a treated layeredcompound to form a polymeric nanocomposite; forming a preform having atleast one layer made from the polymeric nanocomposite; heating thepreform to a first temperature sufficient for blow molding the preform;injection stretch blow molding the preform into an article; wherein thetreated layered compound has been formed by treating a layered compoundwith an organic compound to produce the treated layered compound havingan affinity with the polystyrene based polymer prior to mixing; whereinthe organic compound comprises a ring structured group or a methacrylategroup selected from the group consisting of butyl methacrylate,cyclohexane, methyl styrene, cyclopentane, chlorotoluene, methylmethacrylate, xylene, toluene, vinyl toluene, benzene,methylcyclohexanone, styrene, furan, chlorobenzene, cyclohexanone,dichlorobenzene, nitrobenzene, iodobenzene, cyclopentanone,cyclobutanedione, and combinations thereof; wherein the layered compoundimproves the preform heating efficiency and the first temperature is atleast 5° F. higher than the temperature of an identical preform withoutthe layered compound when heated under the same conditions; wherein theheating of the preform results in a shrinkage of less than 40% and awarpage of less than 8%.
 27. The method of claim 26, wherein the mixingcomprises at least one of the processes of: compounding the polystyrenebased polymer and the treated layered compound; solution mixing thepolystyrene based polymer and the treated layered compound in a solvent;or mixing the treated layered compound with a styrene based monomerprior to polymerization.
 28. The method of claim 14, wherein the organiccompound comprises a ring structured group or a methacrylate groupselected from the group consisting of: butyl methacrylate, cyclohexane,methyl styrene, cyclopentane, chlorotoluene, xylene, toluene, vinyltoluene, benzene, methylcyclohexanone, styrene, furan, chlorobenzene,cyclohexanone, dichlorobenzene, nitrobenzene, iodobenzene,cyclopentanone, cyclobutanedione, and combinations thereof.
 29. Themethod of claim 14, wherein the organic compound comprises a ringstructured group or a methacrylate group selected from the groupconsisting of: cyclohexane, methyl styrene, cyclopentane, chlorotoluene,methyl methacrylate, xylene, toluene, vinyl toluene, benzene,methylcyclohexanone, styrene, furan, chlorobenzene, cyclohexanone,dichlorobenzene, nitrobenzene, iodobenzene, cyclopentanone,cyclobutanedione, and combinations thereof.
 30. The method of claim 14,wherein the organic compound comprises a ring structured group or amethacrylate group selected from the group consisting of: cyclohexane,methyl styrene, cyclopentane, chlorotoluene, xylene, toluene, vinyltoluene, benzene, methylcyclohexanone, styrene, furan, chlorobenzene,cyclohexanone, dichlorobenzene, nitrobenzene, iodobenzene,cyclopentanone, cyclobutanedione, and combinations thereof.
 31. Themethod of claim 14, wherein the layered compound comprises anorganoclay.
 32. The method of claim 14, wherein the polystyrene basedpolymer comprises a homopolymer or a styrenic polymer with one or morecomonomers, and wherein the polystyrene based polymer is present in thenanocomposite in an amount of from 90 wt. % to 99.5 wt. % based on thetotal weight of the nanocomposite.
 33. The method of claim 14, whereinthe polystyrene based polymer further comprises an elastomeric phasethat is embedded in a polymer matrix, wherein the elastomeric phase isselected from one or more of a conjugated diene monomer, an aliphaticconjugated diene monomer, and blends or copolymers of the dienemonomers, and wherein the elastomeric phase is present in thepolystyrene based polymer in an amount ranging from 0.1 wt. % to 10 wt.%.
 34. The method of claim 14, wherein the injection blow molding of thepreform into the article comprises a co-injection blow molding process.35. The method of claim 14, wherein the injection blow molding of thepreform into the article comprises a single or double stage injectionblow molding process.
 36. A preform useful in blow molding processescomprising: a nanocomposite comprising a polystyrene based polymer and alayered compound; wherein the layered compound is treated with anorganic compound to thereby form a material having an affinity withstyrene; and wherein the organic compound comprises a ring structuredgroup or a methacrylate group selected from the group consisting ofbutyl methacrylate, cyclohexane, methyl styrene, cyclopentane,chlorotoluene, methyl methacrylate, xylene, toluene, vinyl toluene,benzene, methylcyclohexanone, styrene, furan, chlorobenzene,cyclohexanone, dichlorobenzene, nitrobenzene, iodobenzene,cyclopentanone, cyclobutanedione, and combinations thereof.